Lithium ferrite catalysed oxidative dehydrogenation process

ABSTRACT

Oxidative dehydrogenation catalysts containing lithium, iron and oxygen, with or without aluminum or chromium, and containing the corresponding ferrite, give superior results and operate at generally lower temperatures than many other ferrite oxidative dehydrogenation catalysts.

This is a division, of application Ser. No. 578,538 filed May 19, 1975,now U.S. Pat. No. 3,998,757.

BACKGROUND OF THE INVENTION

The present invention relates to oxidative dehydrogenation catalystscontaining lithium iron and oxygen and the process of oxidativedehydrogenation using these catalysts. More particularly, the catalystsare ferrites.

Oxidative dehydrogenations employing ferrite catalysts are well known.U.S. Pat. Nos. 3,270,080; 3,284,536; 3,303,234; 3,303,235; 3,303,236;3,303,238; 3,308,182; 3,324,195; 3,334,152; 3,342,890; 3,398,100;3,450;787; 3,420,911; 3,420,912; 3,428,703 and 3,440,299 disclose suchprocesses.

Some prophetic disclosures concerning ferrites tended to regard lithiumequivalent to a number of other metals in forming ferrites useful foroxidative dehydrogenation, e.g., U.S. Pat. Nos. 3,666,684; 3,670,042;3,686,347; 3,702,875; 3,743,683; 3,751,512; 3,780,126 and 3,843,745,which all contain substantially the same disclosure in regard tolithium.

In the present application which deals specifically with the lithiumferrite species critical perimeters and combinations have beendiscovered, which were not considered, investigated, noted, or suggestedby the prior art.

SUMMARY OF THE INVENTION

This invention relates to novel oxidation dehydrogenation catalysts andthe process of oxidative dehydrogenation using the catalysts. Briefly,the catalyst composition for use in oxidative dehydrogenation whichconsist essentially of lithium, iron and oxygen, wherein the mole ratioof lithium to iron is between 2/5 and 1/7, preferably about 1/4 to 1/6,or about 1/5 to 1/5.5, and the surface area of the catalyst is greaterthan 8.1 m² /gram, preferably 10.5 m² /gram or more. Normally thesurface area of the catalyst will not exceed about 200 m² /gram.Aluminum and/or chromium may be substituted for a portion of the iron.Up to about 48 mole %, preferably about 40 mole %, of the iron may bereplaced with Al⁺⁺⁺ or Cr⁺⁺⁺ and have substantially the same catalystactivity, but at lower inlet temperatures.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst of the present invention contain lithium, iron, and oxygenor lithium, iron, oxygen, and aluminum or chromium as described above.The iron and any aluminum or chromium substituted in the composition foriron has a +3 valence. The catalyst of the present invention compriseferrites which are spinel crystalline compositions of the lithium, iron,oxygen, and aluminum or chromium. A preferred catalyst of this type isthat having a face-centered cubic form of crystalline structure.

Lithium and iron form binary spinels of the Li_(1/2) ⁺ Fe_(5/2) ⁺⁺⁺ O₄.Similarly, aluminum and chromium form these compounds with lithium andiron.

In the close-packed array of oxygen ions of the cubic spinel in thestructure (which derives its name from the mineral MgAl₂ O₄) two typesof interstitial sites occur: tetrahedral and octahedral, there being 64and 32 sites, respectively, of which only 8 and 16, respectively areoccupied. The tetrahedral sites are relatively small and generally willnot provide sufficient space for the metal ions without expanding thesite. This expansion is accomplished in the spinel by a displacement ofthe four oxygen ions away from the metal ions along the body diagonalsof the octants having central metal ions. Whereas, the oxygen ions inthe "octahedral octant" are displaced in such a way that this oxygentetrahedron shrinks by the same amount as the metal tetrahedron expands.Thus, cubic symmetry is preserved.

It has been found that some other metals which form binary compounds ofthe spinel structure are not suitable or equivalent in the presentcompositions to the listed metals. For example, Na and K are notsuitable substitutes for Li and produce inactive catalysts. Similarly,Cu⁺¹ decreases the activity of the catalysts.

Ferrite formation may be accomplished by reacting an active compound oriron with an active compound of the designated metals. By activecompound is meant a compound which is reactive under the conditions toform the ferrite, generally oxides, hydroxides or salts. Startingcompounds of iron or the other metals may be such as the nitrates,hydroxides, hydrates, oxalates, carbonates, acetates, formates, halides,oxides, etc. The starting compounds are suitably oxides, or compoundswhich will decompose to oxides during the formation of the ferrite suchas organic salts and inorganic salts or hydroxides. For example, lithiumoxalate may be reacted with iron oxide hydrates to form lithium ferrite.Salts of the desired metals may be coprecipitated and the precipitateheated to form the ferrite. Desired ferrites may be obtained byconducting the reaction to form the ferrite at relatively lowtemperatures, that is, at temperatures lower than some of the very hightemperatures used for the formation of some of the semi-conductorapplication. Good results, e.g., have been obtained by heating theingredients to a temperature high enough to produce the requiredferrite, but a conditions no more severe than equivalent to heating at950° C or 1000° C for 90 minutes in air and generally the maximumtemperature will be less than 1300° C and preferably less than 1150° C.Methods adapted for preparing catalysts suitable for this invention aredisclosed in U.S. Pat. Nos. 3,270,080; 3,284,536; 3,303,234-6;3,303,238; 3,308,182; 3,334,152; 3,342,890; 3,686,347; 3,450,787; and,3,843,745 and these disclosures are hereby incorporated by reference.

The catalyst compositions may contain an excess of either iron orlithium over the stoichiometric amount to form the ferrite. Furthermore,there may be unreacted lithium ferrite precursors present in thecompositions in addition to the ferrite.

The present catalyst compositions have been found to exhibit a certaintype of X-ray diffraction pattern. The compositions do not have anysharp X-ray diffraction reflection peaks as would be found, e.g., in ahighly crystalline material having the same chemical composition.Instead, the compositions of this invention exhibit reflection peakswhich are relatively broad. The degree of sharpness of the reflectionpeak may be measured by the reflection peak bank width at half height(Wh/2). In other words, the width of the reflection peak as measured atone half of the distance to the top of the peak is the "band width athalf height". The band width at half height is measured in units of °2theta. Techniques for measuring the band widths are discussed, e.g., inChapter 9 of Klug and Alexander, X-ray Diffraction Procedures, JohnWiley and Son, N.Y., 1954. The observed band widths at half height ofthe preferred compositions of this invention are at least 0.16° 2 thetaand normally will be at least 0.20° 2 theta. For instance, excellentcompositions have been made with band widths at half height of at least0.22° or 0.23° 2 theta. The particular reflection peak used to measurethe band width at one-half height is the reflection peak having Miller(hkl) indices of 220. (See, e.g., Chapter of Klug and Alexander, ibid).Applicants do not wish to be limited to any theory of the invention inregard to the relationship between composition activity and band width.The catalyst composition may also include inert binding agents andcarriers or supports for the catalyst, such as alumina, pumice, silicaand so forth, but these will not ordinarily exceed about 80 percent or90 percent by weight of the catalytic composition including activecatalyst components and inert binding agents or fillers. The catalystwill be by definition present in a catalytic amount. The amount ofcatalyst ordinarily will be greater than ten square feet of catalystsurface per cubic foot of reaction zone containing catalyst. The term"catalysts", as used herein, means total active catalyst components anddoes not include inert binding agents or fillers. Of course, the amountof catalyst may be much greater, particularly, when irregular surfacecatalyst is used. When the catalyst is in the form of particles, eithersupported or unsupported, the amount of catalyst surface may beexpressed in terms of the surface area per unit weight. The ratio ofcatalyst surface to weight will be dependent upon several factors,including the particle size distribution, apparent bulk density of theparticles, the carrier, etc. Stated otherwise, the compositions referredto in this application are the main active constituents of thedehydrogenation process during dehydrogenation and any ratios andpercentages refer to the surface of the catalyst in contact with thegaseous phase during dehydrogenation.

The compositions of this invention may also comprise additives, such asdisclosed in U.S. Pat. No. 3,270,080 and U.S. Pat. No. 3,303,238.Phosphorus, silicon, boron, sulfur, or mixtures thereof are examples ofadditives. These additives are added to the preformed ferrites usuallyby slurrying the ferrite and the additive, such as phosphoric acid, inthe desired ratio. Polyvinyl alcohol may be advantageously employed informing the catalyst into useable configurations such as extrudedpellets.

The catalysts may be activated or regenerated by reducing with areducing gas, e.g., such as hydrogen or hydrocarbons. For example, thepreformed compositions may be reduced with, e.g., hydrogen at atemperature of at least 250° C with the temperature of reductiongenerally being no greater than 850° C. The period of time for reductionwill be dependent somewhat on the temperature of reduction.

The process of this invention may be applied to the dehydrogenation of awide variety of organic compounds. Such compounds normally will havefrom 2 to 20 carbon atoms, at least one ##STR1## grouping, a boilingpoint below about 350° C, and such compounds may contain other elements,in addition to carbon and hydrogen such as oxygen, halogens, nitrogenand sulfur. A preferred group of organic reactants are hydrocarbons.Preferred are compounds having 2 to 12 carbon atoms, and especiallypreferred are compounds of 3 to 6 or 8 carbon atoms.

Among the types of organic compounds which may be dehydrogenated bymeans of the process of this invention are nitriles, amines, alkylhalides, ethers, esters, aldehydes, ketones, alcohols, acids, alkylaromatic compounds, alkyl heterocyclic compounds, cycloalkanes, alkanes,alkenes, and the like. Illustration of dehydrogenations includepropionitrile to acrylonitrile; propionaldehyde to acrolein; ethylchloride to vinyl chloride; methyl isobutyrate to methyl methacrylate; 2or 3 chlorobutene-1 or 2; 2, 3-dichlorobutane to chloroprene; ethylpyridine to vinyl pyridine; ethylbenzene to styrene; isopropylbenzene toα-methyl styrene; ethylcyclohexane to styrene; cyclohexane to benzene;ethane to ethylene or acetylene; propane to propylene, methyl acetylene,allene, or benzene; isobutane to isobutylene; n-butane to butene andbutadiene-1, 3; n-butene to butadiene-1, 3, and vinyl acetylene; methylbutene to isprene; cyclopentane to cyclopentene and cyclopentadiene;n-octane to ethyl benzene and ortho-xylene; monomethylheptanes toxylenes; ethyl acetate to vinyl acetate; 2, 4, 4-trimethylpentane toxylenes; and the like. Some representative materials which may bedehydrogenated by the novel process of this invention include ethyltoluene, alkyl chlorobenzenes, ethyl naphthalene, isobutyronitrile,propyl chloride, isobutyl chloride, ethyl fluoride, ethyl bromide,n-pentyl iodide, ethyl dichloride, 1, 3 dichlorobutane, 1,4dichlorobutane, the chlorofluoroethanes, methyl pentane, methylethylketone, diethyl ketone; n-butyl alcohol, methyl propionate and the like.

Illustrative dehydrogenation reactions are the following: Acycliccompounds having 4 to 5 contiguous carbon atoms to the correspondingolefins, diolefins or acetylenes having the same number of carbon atoms;aliphatic hydrocarbons having 6 to 16 carbon atoms and at least onequaternary carbon atom to aromatic compounds, such as 2, 4,4-trimethylpentene-1 to a mixture of xylenes; acyclic compounds having 6to 16 carbon atoms and no quaternary carbon atoms to aromatic compoundssuch as n-hexenes to benzene; cycloparaffins and cycloolefins having 5to 8 carbon atoms to the corresponding olefin, diolefin or aromaticcompound, e.g., cyclohexane to cyclohexene or cyclohexadiene or benzene;aromatic compounds having 8 to 12 carbon atoms including one or twoalkyl side chains of 2 to 3 carbon atoms to the corresponding aromaticwith unsaturated side chain such as ethyl benzene to styrene.

The preferred compounds to be dehydrogenated are hydrocarbons with aparticularly preferred class being acyclic hydrocarbons having 4 to 5contiguous carbon atoms or ethyl benzene and the preferred products arebutene-1 or 2, butadiene-1, 3, vinyl acetylene, 2-methyl-1-butene,3-methyl-1-butene, 2-methyl-2-butene, isoprene, styrene or mixturesthereof. Especially preferred as feed are butene-1 or 2 and the methylbutenes and mixtures thereof such as hydrocarbon mixtures containingthese compounds in at least 50 mol percent.

The dehydrogenation reaction may be carried out at atmospheric pressure,superatmospheric pressure or at sub-atmospheric pressure. The totalpressure of the system will normally be about or in excess ofatmospheric pressure, although sub-atmospheric pressure may alsodesirably be used. Generally, the total pressure will be between about 4p.s.i.a. and about 100 or 125 p.s.i.a. Preferably, the total pressurewill be less than about 75 p.s.i.a. and excellent results are obtainedat about atmospheric pressure.

The organic compound to be dehydrogenated is contacted with oxygen inorder for the oxygen to oxidatively dehydrogenate the compound. Oxygenmay be fed to the reactor as pure oxygen, as air, as oxygen-enrichedair, oxygen mixed with diluents, solid oxidants, and so forth. Oxygenmay also be added in increments to the dehydrogenation zone. Althoughdeterminations regarding the mechanism of reaction are difficult, theprocess of this invention is an oxidative dehydrogenation processwherein the apparent mechanism of this invention is the reaction ofoxygen with hydrogen released from the hydrocarbon.

The amount of oxygen employed may vary depending upon the desired resultsuch as conversion, selectivity and the number of hydrogen atoms beingremoved. Thus, to dehydrogenate butane to butene requires less oxygenthan does the reaction that proceeds to produce butadiene. Normally,oxygen will be supplied (including all sources, e.g., air to thereactor) in the dehydrogenation zone in an amount from about 0.2 to 1.5,preferably 0.3 to 1.2, mols per mol of H₂ being liberated from theorganic compound. Ordinarily the mols of oxygen supplied will be in therange of from .2 to 2.0 mols per mol of organic compound to bedehydrogenated and for most dehydrogenations this will be within therange of .25 to 1.5 mols of oxygen per mol of organic compound.

Preferably, the reaction mixture contains a quantity of steam or diluentsuch as nitrogen with the range generally being between about 2 and 40mols of steam per mol of organic compound to be dehydrogenated.Preferably, steam will be present in an amount from about 3 to 35 molsper mol of organic compound to be dehydrogenated and excellent resultshave been obtained within the range of about 5 to about 30 mols of steamper mol of organic compound to be dehydrogenated. The functions of thesteam are several-fold, and the steam may not merely act as a diluent.Diluents generally may be used in the same quantities as specified forthe steam. These gases serve also to reduce the partial pressure of theorganic compound.

Halogen may also be present in the reaction gases to give excellentresults. The presence of halogen in the dehydrogenation zone isparticularly effective when the compound to be dehydrogenated issaturated, such as a saturated hydrocarbon. The halogen present in thedehydrogenation zone may be either elemental halogen or any compound ofhalogen which would liberate halogen under the conditions of reaction.Suitable sources of halogen are such as hydrogen iodide, hydrogenbromide and hydrogen chloride; aliphatic halides, such as ethyl iodide,methyl bromide, methyl chloride, 1, 2-dibromo ethane, cycloaliphatichalides, ammonium iodide, ammonium bromide; ammonium chloride, sulfurylchloride; and the like. The amount of halogen, calculated as elementalhalogen, may be as little as about 0.0001 or less mol of halogen per molof the organic compound to be dehydrogenated to as high as 0.2 or 0.5.

The temperature for the dehydrogenation reaction generally will be atleast about 200° C, such as greater than about 250° C or 275° C, and themaximum temperature in the reactor may be about 700° C or 800° C orperhaps higher such as 900° C under certain circumstances. However,excellent results are obtained within the range of or about 250° C to600° C, such as from or about 300° C to or about 500° C. Thetemperatures are measured at the maximum temperature in thedehydrogenation zone.

The gaseous reactants may be conducted through the reaction chamber at afairly wide range of flow rates. The optimum flow rate will be dependentupon such variables as the temperature of reaction, pressure, particlesize, and so forth. Desirable flow rates may be established by oneskilled in the art. Generally, the flow rates will be within the rangeof about 0.10 to 10 liquid volumes of the organic compound to bedehydrogenated per volume of dehydrogenation zone containing catalystper hour (referred to as LHSV). Usually, the LHSV will be between 0.15and about 5. for calculation, the volume of a fixed bed dehydrogenationzone containing catalyst is that original void volume of reactor spacecontaining catalyst.

The process of this invention utilizes either a fixed bed or moving bed,such as a fluidized catalyst, reactor. Reactors which have been used forthe dehydrogenation of hydrocarbons by non-oxidative dehydrogenation aresatisfactory such as the reactors for the dehydrogenation of n-butene tobutadiene-1, 3. Although means to remove heat from the reactor may beemployed, such as coils, the invention is particularly useful withessentially adiabatic reactors where heat removal is a problem.

The following examples are only illustrative of the invention and arenot intended to limit the invention. All percentages are weight percentunless specified otherwise. All conversions (C), selectivities (S) andyields (Y) are expressed in mol percent of the designated feed.

In all of examples 1-19 encompassing the invention as disclosed, thepresence of lithium ferrite was determined by X-ray analysis,* ferromagnetism, color change or a combination of these.

EXAMPLES 1 - 5

In these first runs the effectiveness of lithium ferrite as an oxidativedehydrogenation catalyst (butene-2 to yield butadiene) is demonstrated.A second discovery from these runs was the catalysts having surfaceareas of 8.1 or less are inferior or inoperable. Catalysts havingsurface area of 8.1 m² /g. or less and otherwise comparable to thosehaving greater surface area are active, but are unstable and have veryshort useful lives. The catalysts in these examples were prepared byslurrying Fe₂ O₃.H₂ O/Li₂ C₂ O₄ in water drying at about 100° C forabout 16 hours and calcining for two hours in air (100 ml/min.) and weresupported on 7-9 mesh AMC alumina by slurrying the alumina (60%) andactives (38.8%) with H₃ PO₄ (1.2%). The feed for oxidativedehydrogenation was 98%+butene-2 to produce butadiene (Bd). It should beappreciated by those of skill in the art that the selection of highpurity butene-2 to produce butadiene is not a restriction on theoperable feeds or the products in the process, but was made, forexample, to provide comparable results, availability, calibration ofanalytical equipment, and standardization of analytical procedures. Theratio of hydrocarbon (butene-2) to oxygen to steam for each example was1/0.55/15 and the LHSV was 1.5.

The apparatus employed was a one inch Vycor reactor, into which 25 cc ofcatalyst was placed, equipped with a receiving flask and condenser andheated with a cylindrical furnace assembly. Steam, butene-2 and air aremixed in the reactor head and brought up to the desired temperature inthe upper portion of the reactor (which contained about 13 inches ofquartz chips). The 25 cc catalyst bed was supported on about 3 inches ofquartz chips. Temperatures in the reactor were determined bythermocouples. Table I provides additional information on catalyst andoperating conditions and sets forth the results.

                                      TABLE I                                     __________________________________________________________________________    Oxidative Dehydrogenation of Butene-2 Over Lithium Ferrites.sup.(1)           __________________________________________________________________________    Catalyst                Process Conditions                                                                        Results                                        Li/Fe Calc. Temp.                                                                          Surf Area                                                                           T.sub.i                                                                           T.sub.max                                                                        Hours on                                                                           mole %                                    Example                                                                            mole ratio                                                                          (° C)                                                                         (m.sup.2 /g)                                                                        (° C)                                                                      (° C)                                                                     Steam(.sup.2)                                                                      C/S/Y.sub.Bd.                             __________________________________________________________________________    1..sup.(6)                                                                         1/5   600    10.5  349 477                                                                              31/2 59/95/56                                                          357 505                                                                              (31/2).sup.+ 5                                                                     58/94/55                                  2.   1/5   700    8.1          (4).sup.+ 3)                                                                       --.sup.(3)                                3.   1/5   550    11.7  361 533                                                                              3    59/93/55                                                          250 485                                                                              4    60/94/56                                  4..sup.(4)                                                                         1/5   600    10.5  360 481                                                                              41/2 62/94/58                                  5.   1/5.5.sup.(5)                                                                       600    3.6   402 458                                                                              1/2  41/95/89                                                          various                                                                              (11/2+2)                                                                           --.sup.(3)                                __________________________________________________________________________     .sup.(1) All catalysts were reduced with H.sub.2 /steam at 550° C      prior to run.                                                                 .sup.(2) Hours on stream from previous day are indicated in parentheses.      The system was left under N.sub.2 at˜ 350° C overnight when      run a second day.                                                             .sup.(3) Unstable.                                                            .sup.(4) Repeat of preparation used for Example 1.                            .sup.(5) Excess Fe used as FeCl.sub.3.                                        .sup.(6) Presence of lithium ferrite verified by X-ray analysis.         

EXAMPLES 6 - 9

These examples demonstrate the criticality of the Li/Fe mole ratio.Catalyst preparation reactants and operating conditions were the same asin Examples 1 - 5. The difference being the mole ratios of Li/Fe. Thedata shows inferior catalyst in terms of yields at ratios of Li/Fe 2/5and 1/7; however, within this range excellent catalysts are produced.The catalyst and results are set out in Table II.

                  TABLE II                                                        ______________________________________                                        Catalyst Li/Fe                                                                         Calci-                                                               Li/Fe    nation          Process Conditions                                                                         Results                                 Ex.  mole    atmos-  Temp. T.sub.i                                                                            T.sub.max                                                                          Hours on                                                                             mole %                            No.  ratio   phere   (° C)                                                                        (° C)                                                                       (° C)                                                                       Steam  C/S/Y.sub.Bd.                     ______________________________________                                        6.*  2/5     air     600   410  535  1/4    26/74/19                          1.*  1/5     air     600   349  477  31/2   59/95/56                          4.   1/5     air     600   360  481  41/2   62/94/58                          7.   1/5.5   air     600   355  482  31/4   61/94/57                          8.   1/5.5   N.sub.2 600   326  470  31/4   61/94/57                          9.   1/7     air     600   359  468  31/4   41/94/39                          ______________________________________                                         *Presence of lithium ferrite verified by X-ray analysis.                 

EXAMPLES 10 - 19

These examples demonstrate that aluminum and chromium may be substitutedfor a portion of the iron in the present catalyst. The catalystpreparations were the same as examples 1 - 5, as were the conditions ofthe oxidation dehydrogenations. The aluminum substituted compositionsare shown in Table III along with the results. The runs on chromiumsubstituted lithium ferrite are set out in Table IV. Note the low inlettemperatures.

                  TABLE III                                                       ______________________________________                                        Oxidative Dehydrogenation of Butene-2 Over                                    (Li 0.5) (Fe.sub.y Al.sub.2.5 5-y)O.sub.4 *                                   Catalysts                                                                     Example                                                                              mole %          Process Conditions                                                                          Results                                  No.    Al*      "y"    T.sub.i, (° C)                                                                 T.sub.max, (° C)                                                               C/S/Y.sub.Bd.                          ______________________________________                                        10.    20       2.0    292     475     58/94/55                               11.    40       1.5    297     478     60/94/56                               12.    60       1.0    376     485     53/92/49                               ______________________________________                                         *Based of Fe replaced.                                                        *Catalysts were prepared by calcining Fe.sub.2 O.sub.3 . H.sub.2              O/Li.sub.2 C.sub.2 O.sub.4 /Al(OH).sub.3, blends for two hours in air at      600° C. All catalysts were supported on AMC with 3%H.sub.3 PO.sub.     (40% actives). HC/O.sub.2 /S employed was 1/0.55/15, at an LHSV of 1/5        (>98% butene-2 feed). All catalysts were reduced with H.sub.2 /steam at       550° C prior to run.                                              

                  TABLE IV                                                        ______________________________________                                        OXIDATIVE DEHYDROGENATION                                                     OF BUTENE-2 OVER Li.sub.0.5 Cr.sub.x Fe.sub.2.5-x O.sub.4.sup.(1)                            Process Conditions                                             Ex-   Catalysts                Approx.                                                                               Results                                ample mole %          Calc.                                                                              T.sub.i                                                                            T.sub.max                                                                          Hrs. on                                                                              mole %                            No.   Cr.sup.(3)                                                                             "x"    Atm. (° C)                                                                       (° C)                                                                       stream.sup.(2)                                                                       C/S/Y.sub.Bd.                     ______________________________________                                        13.   40       1.0    air  200  442  4      50/91/46                          14.   40       1.0    N.sub.2                                                                            297  445  21/2   53/94/50                          15.   20       0.5    N.sub.2                                                                            250  443  (31/2)+1/2                                                                           54/92/50                          16.   20       0.5    air  350  480  1/2    51/91/46                          17.   20       0.5    air  298  455  1      54/92/50                          18.   50       1.25   N.sub.2                                                                            244  415  21/2   53/92/49                          19.   50       1.25   air  250  435  3      57/92/49                          ______________________________________                                         .sup.(1) Catalysts were prepared by calcining Li.sub.2 C.sub.2 O.sub.4        /Fe.sub.2 O.sub.3 . H.sub.2 O/Cr.sub.2 O.sub.3 . xH.sub.2 O blends at         600° C for two hours in either air or N.sub.2 100 ml/min. for          both), and were supported on AMC with 3 %H.sub.3 PO.sub.4 (40 % actives),     HC/O.sub.2 /S ratio employed was 1/0.55/15, the LHSV was 1.5, and all         catalysts were reduced with H.sub.2 /steam at 550° C prior to run.     .sup. (2) Hours on stream from previous day are indicated in parentheses.     The system was left under N.sub.2 at 250° C overnight.                 .sup. (3) Based on Fe replaced.                                          

EXAMPLES 20 - 22

These examples demonstrate the non-equivalence of sodium and potassiumto lithium in the present catalyst. Copper of valence + 1 is also shownto be non-equivalent to + 1 valent lithium. The same slurry techniquewas used to produce the catalyst compositions, which were calcined ineither air or nitrogen and deposited on 7 - 9 mesh alumina with 1.2% H₃PO₄ (unless otherwise indicated). The hydrocarbon feed was 98 + %butene-2 at the HC/O₂ /S ratio 1/0.55/15; LHSV 1.5. Table IV sets outthe catalysts and the results.

                                      TABLE V                                     __________________________________________________________________________    COMPARATIVE CATALYSTS COMPOSITION                                             Catalysts             Process Conditions                                      Example                                                                            Composition                        Hours on                                                                           Results                          No.  mole ratio  Atmosp.                                                                            Temp° C                                                                      T.sub.i (° C)                                                                T.sub.max (° C)                                                              Steam                                                                              C/S/Y.sub.Bd                                                                         Remarks                   __________________________________________________________________________    20.  LiNa ferrite.sup.1                                                                        air  600   450   --    11/2 --     inactive                       Li/Na/Fe-0.7/0.3/5                                                                                                           low butene                21.  K.sub.2 0.6Fe.sub.2 O.sub.3.sup.2,3                                                       air  900   450   530   21/2 --     version                        K/Fe-1/6.6                                     31/2%CO.sub.2,                                                                no butadiene              22.  LiCu ferrite.sup.4                                                                        N.sub.2                                                                            600   342   490   21/2 32/74/25                                                                             poor selectivity               Li/Cu/Fe-0.5/0.5/5                                                       __________________________________________________________________________      *All catalyst were reduced with H.sub.2 /steam at 550° C prior to     run.                                                                          .sup.1 Na.sub.2 CO.sub.4 used in slurry prep.                                 .sup.2 K.sub.2 CO.sub.3 used in slurry prep.                                  .sup.3 K and Fe do not form a spinel analogons to Li-Fe, prep. suggested      by U.S. Pat. No. 3,766,191.                                                   .sup.4 Cu.sub.2 O used in slurry prep.                                   

The invention claimed is:
 1. A process for oxidative dehydrogenationcomprising contacting oxygen and organic compounds having 2 to 20 carbonatoms, at least one ##STR2##grouping and boiling point below about 350°C, in vapor phase at a temperature of at least about 250° C in thepresence of a catalyst composition containing a lithium ferriteconsisting essentially of lithium, iron and oxygen; lithium, iron oxygenand aluminum or chromium; or lithium, iron, oxygen, aluminum andchromium the mole ratio of lithium to iron being in the range between2:5 to 1:7, said catalyst composition having a surface area of at least8.1 m² /gram.
 2. The process according to claim 1 wherein aluminum orchromium may comprise up to 48 mole % of the total of iron, aluminum orchromium present in said catalyst.
 3. The process according to claim 2wherein the aluminum or chromium may comprise up to about 40 mole % ofthe total of iron, aluminum or chromium.
 4. The process according toclaim 1 wherein the mole ratio of lithium to iron is in the range of 1:4to 1:6.
 5. The process according to claim 1 wherein said organiccompounds comprise hydrocarbons.
 6. The process according to claim 1wherein a product is recovered, corresponding to said organic compoundsand having a higher degree of ethylenic unsaturation than said organiccompounds.
 7. The process according to claim 1 wherein said catalystcomposition consists essentially of lithium, iron and oxygen.
 8. Theprocess according to claim 1 wherein said catalyst composition consistsessentially of lithium, iron, oxygen and aluminum or chromium.
 9. Theprocess according to claim 8 wherein said catalyst composition consistsessentially of lithium, iron, oxygen and aluminum.
 10. The processaccording to claim 8 wherein said catalyst composition consistsessentially of lithium, iron, oxygen and chromium.
 11. The processaccording to claim 1 wherein the catalyst composition has a surface areaof at least 10.5 m² /gram.